Personally, I think Brotherhood is currently the winner in terms of value.
Animus 1.0:
Contents: 1 new multiplayer game mode, 1 new map.
Price: Free.
Animus 2.0:
Contents: 1 new multiplayer game mode, 1 new map.
Price: Free.
Dusk / Night Maps:
Contents: two reskins of existing maps - Rome and Venice.
Price: Free (earned by the community for racking up an obsurd number of games played and/or kills made).
Animus 3.0:
Contents: 2 new multiplayer modes, 1 new map, four new characters, unlocks for both Limited Edition characters (if you didn't already have them), patch to allow all multiplayer modes to work on all maps (including the ones in the previous DLC packs), a new single-player story arc, two Limited Edition mission unlocks (if you didn't already have them), Limited Edition armour unlock (if you didn't already have it).
Price: £7.99
Yeah... I am going to go ahead and say that is good value from Ubisoft! In particular, I really, really respect them for what they did. The Dusk / Night Map thing was cool, the Animus expansions were great, and then when they finally make us pay for our expansion they not only throw in a big dollop of single-player content, they go back and patch the old stuff AND produce the most awesome game mode I've ever seen.
That is how DLC should be done.